Effects of Postharvest Storage on Cyanide Content and Activity of Partially Purified Rhodanese from Bitter Cassava (Manihot Utilissima) Tubers
This research investigated the effects of postharvest storage on cyanide content and rhodanese isolated from bitter cassava (Manihot Utilissima) tubers. Cyanide content of freshly harvested sample, samples stored for 4 days and samples stored for 8 days were estimated by silver nitrate titration method. Rhodanese was purified using 80% ammonium sulphate precipitate and ion-exchange chromatography on CM-Sephadex C-25.Cyanide content from freshly harvested sample was 345.6 mg HCN/kg while 237.6 mg HCN/kg and 108 mg HCN/kg were obtained for samples stored for 4 days and samples stored for 8 days respectively. Specific activity of rhodanese from freshly harvested sample was 3.411 RU/mg while 5.92 RU/mg and 5.35 RU/mg were obtained for samples stored for 4 days and samples stored for 8 days respectively. The Km values of rhodanese for KCN were 3.18 mM, 2.40 mM, 0.25 mM for freshly harvested sample, samples stored for 4 days and samples stored for 8 days respectively. The optimum temperature from freshly harvested sample and sample stored for 4 days was 70 0C while samples stored for 8 days was 50 0C. An optimum pH of 4.0 was obtained from the 3 samples.Rhodanese play plausible role in cyanide reduction during the postharvest storage.